Little wings of desire

One of the joys of having a patch of wildlife garden, even if it is small like ours, is sitting in the sun and watching the species that visit it. Often they are familiar - our pond attracts damselflies and dragoflies, and we try to include a wide range of pollinator-friendly plants for bees and hoverflies, but sometimes something a little different appears. In this case a little flicker of movement caught my eye and I looked closer to see two small flies waving their wings at each other. The wings had dark patterns of blotches and lines and I recognised them as being in the family Tephritidae. This family has no common name as such, but they are sometimes considered to be 'fruit flies' in the broad sense, and are also included in the informal grouping known as 'picture-winged flies'. A little more research in Smit (2010) and White (1988) confirmed the species as Tephritis neesii, which is common on Leucanthemum (e.g. ox-eye daisies as here) in southern England, where I live. So, nothing unusual as such, but I'd not seen it before; I did wonder if the 'dance' was a form of competition between males, but it is actually a male-female mating display.

Pair of Tephritis neesii during their mating dance.

It also turns out that in some tephritids, the form of the dance can indicate the genus of the fly - Tephritis such as these hold their wings flat and open/close them alternately; Urophora open/close them simultaneously while rocking from side to side; Chaetorella hold their wings sideways with the edge pointing up, then shake them. Males do fight, but it is less elegant - there was a third fly just out of shot that buzzed one of the pair later on. Though my photo shows the wing pattern quite clearly (it's the same in males and females), a video shows the dance itself, so here's one that's been kindly posted on YouTube:



References

Smit, J.T. (2010). De Nederlandse boorvliegen (Tephritidae). Entomologische Tabellen. Supplement bij Nederlandse Faunistische Mededelingen, 5: 1–159. [In Dutch]
White, I.M. (1988). Tephritid flies. Diptera: Tephritidae. Handbooks for the Identification of British Insects 10(5a): 1–134.

In spring the pond goes sproing

After a long, cold early spring, the last couple of weeks have been warm, dry and sunny - and the season has leapt at the opportunity. Butterflies are flying, birds are nest-building, bees are pollinating. All good things. As a microcosm of this rapid seasonal burst of activity the denizens of our garden pond have been distracting me from computer-based tapping and drawing me out to sit by and watch, camera in hand. Our pond's not huge, but a lot of care was taken to ensure variety of structure (and thus habitat) - here are a few of the occupants taking advantage of it.

The fly Elgiva cucularia. It is a member of the family Sciomyzidae that specialise in hunting snails - of which we have plenty. This species is associated with boggy conditions and I have recorded it several times on our pond vegetation, so the shallow, algae filled section is clearly doing its job.

A Large Red Damselfly Pyrrhosoma nymphula posing obligingly on my finger.

One of at least six smooth newts living in our pond. This shot was taken with a waterproof endoscope which I'm still new at using.

Some of this year's batch of frogspawn.

Two pond snails busily engaged in making more snails. The whitish structure top-right is indeed a snail penis AKA 'love-dart'.

Long-legged lovers from lakeside leaves

After holidays, after the backlog of work I returned to... it's time for flies - in particular the genus Dolichopus in the family Dolichopodidae (long-legged flies). As well as long legs, most male 'dolis' have very large genitalia, but a post title focusing on that feature might reach the wrong audience... Anyhow, I was watching what I think is D. popularis (there are several similar species in the genus) when I noticed courtship behaviour - so, out came the camera to document a romantic photo-story...

A single Dolichopus

Two males court one female (on the left)

One male is driven off, the other courts the female by standing on long legs over her and rapidly beating his wings.

He tried to mate but was rebuffed (he would dart behind her, but she moved away and turned round), so back to the courting.

This time his efforts were sufficient and the female permits mating.

Female post-mating.

Male post-mating - the large structure bent down from the rear of the abdomen is his genitalia.

Male post-mating.

The moth-mummy returns

I've written about parasitic braconid wasps before, and you know, I probably will again - because they are fascinating. This one hatched recently from the mummified remains of what I think is a small noctuid moth larva that I found in our garden, possibly one of the Xestia or Noctua species.

Mummified remains of an unfortunate moth larva, showing the legs

Mummified moth larva showing the wasp's exit hole at the rear. The material sticking the mummy to its substrate can be seen beneath the head.

As you've gathered, this is an internal parasite (parasitoid) - in this case probably Aleoides borealis or something taxonomically close to it (written as "Aleiodes sp. near borealis"). This kills the host before it is fully grown - it then changes the host behaviour to ensure it adopts a parasite-frindly position, after which the parasitoid makes a slit in the host on the underside near the head. Through this slit, it produces a sticky fluid which glues the host in place. However, I don't only have an empty husk to show you - I collected the mummy before emergence, and this is what appeared in my hatchery.

Aleiodes sp. near borealis

Head (with ocelli) of Aleiodes sp. near borealis

Abdominal pattern of Aleiodes sp. near borealis

Parasitic Hymenoptera are notoriously tricky to identify, but I think this is a reasonable conclusion - as ever, I am happy to hear from anyone who has a better idea what it is!

Red goo of doom

If you've seen and/or read H.G.Wells' War of the Worlds, you'll know about the alien red substance that creeps and raminates... if not, I recommend a library near you. In any case, when I saw a fairly uniform red growth in water on a polythene cover in our garden, (a) my sci-fi nerdery kicked in, and (b) I had to see what it really was.

Mystery red goo in a thin layer of rainwater.

 I did wonder if it was bacteria, and took a sample for a look under the microscope.

At x40, small round red structures are seen.

At x100, these show some faint internal structure.

Using the camera to zoom to about x250, this creature was seen, alive but contracted.

At this point, I knew that is wasn't bacteria (well, I'm sure there is some too) but a rotifer, probably Rotaria sp. These can be found in mud, detritus, among moss and in free-standing water as here. If their thin layer of water dries out they can form resistant cysts and re-emergence when wetted by rain - it is possible the red structures are cysts as rotifers can be very numerous. Rotifers as a whole are small (almost all smaller than 1mm, and some a tenth of this) and found in almost any wet or damp habitat. Some genera are benthic/littoral, some are planktonic, many include both benthic and planktonic species. Most rotifers seen are female and reproduce parthenogenetically (i.e. without needing to mate), while males occur sporadically and often seasonally, and being smaller are less often found. However, males are not known for the bdelloid group in which Rotaria is placed. So, presumably the photos here are all of females!


There isn't space for a detailed look at rotifers here, but if you want to be able to identify British freshwater planktonic species (e.g. those found in ponds), then Pontin (1978) is a good starting point.

While some move with cilia, others, as here have a 'foot' like a mollusc and move using this, being able to contract and expand their body.

Rotaria extended and curled. Various structures are visible - the head is blurred bottom-right - moving left, the paired jaws can be seen.

Rotaria extended, head towards the bottom.

Next post - back to the macroscopic world!

Reference

Pontin, R.M. (1978). A Key to the Freshwater Planktonic and Semi-planktonic Rotifera of the British Isles. FBA, Ambleside.

Beetles love big butts and they cannot lie

Spring means many things - for many species overwintering adults re-emerge and set about the important business of reproduction. One common species that is often seen doing this is the green dock beetle Gastrophysa viridula. It feeds mainly on broad-leaved dock Rumex obtusifolius and related species and in April/May patches of dock can be seen with large numbers of these beetles. Such groups can be highly localised however - one patch of dock can have hundreds of beetles while a nearby patch on the same site seems to have none, possibly due to adults clustering for mate-finding purposes - it is not due to mobility as they can fly. Mating is a competitive activity though as males may try to dislodge rivals, and have foot-pads. These appear white around the sides of the tarsi (feet) to help them grip the female.

Two male G. viridula compete for one female.

Gastrophysa viridula as they are often found - a mating pair.

A dislodged male G. viridula draws its legs in for protection.

The females are particularly distinctive as they have swollen abdomens which extend beyong the elytra (wing cases). There are two or more generations per year (possibly up to six depending on temperature and other conditions) and the oval yellowish eggs can be seen in small clusters. The first new adults emerge in June and others appear through to September. They then overwinter from October to April.

Eggs of G. viridula.

Female G. viridula showing the swollen black abdomen.

The adults chew roundish holes in dock leaves, but the black larvae can skeletonise whole leaves until just a network of veins is left. For this reason, where certain Rumex species are considered invasive, G. viridula has been suggested as a potential biological control, though as ever introducing non-native species needs to be considered very carefully to avoid unwanted impacts on native species.

G. viridula larvae feeding on dock leaf.

Bum-bursting mummy-wasps

Yes, you know it from the title - it's parasite time. If I ever feel that tiny beetles are too easy to identify and I fancy a challenge, the parasitic Hymenoptera are the group of choice - huge numbers of species, tiny differences between them, and few accessible keys. Yay. To make sure I don't get lazy, I have a hatchery where pupae (for example those I dislodge cutting firewood, mending the garden fence etc) are kept to see what they turn out to be as adults, identified and maybe even released. Sometimes other things turn up, for example this mummified larva of the knot-grass moth Acronicta rumicis on a bramble stem.

Mummified larva of Acronicta rumicis

It's worth noting that this is not a pupa - it is the moth larva's empty skin stuck to the stem by the dark brown sticky substance you can see just behind the head. This 'glue' is released by the fully grown wasp larva by cutting a slit in the underside of its host. I have had the 'mummy' in a hatchery for several weeks, but this morning I found an exit hole at the rear of the dead moth larva, and a lively adult wasp scuttling and flying inside the container.

Acronicta rumicis 'mummy' showing the parasite's emergence hole

The parasitic wasp cooled down and quiet. 1 square = 5mm.

So, time for identification. It's a wasp of some sort within the superfamily Ichneumonoidea. However, the abdomen isn't on a thin stalk and the wing venation indicates it is of the family Braconidae rather than Ichneumonidae.

Braconid wasp showing wing venation

For comparison, the wing venation of the braconid Aleiodes praetor, from Huddleston & Gauld (1988)

Now, it's worth noting that there is no guide to British braconid genera or species. Shaw & Huddleston (1991) gives a key to the subfamilies, but beyond that, identification requires a variety of more-or-less obscure journal articles in most cases, and the taxonomy has undergone a lot of revision. Fortunately however, this is (for a braconid) a relatively straightforward specimen. Firstly, the subfamily key takes it to Rogadinae and secondly, the wing diagram above matches the specimen closely because (handily) they are the same - Aleiodes. In the most recent checklist (Broad et al. 2012) there are 37 species of this genus in Britain and all are believed to be solitary (unlike many braconids where many parasites develop in a single host, the best known probably being Cotesia glomerata AKA Apanteles glomeratus). Although species identification is challenging, there are some clues. For example, the first two abdominal segments (blue arrows in the photo below) have longitudinal ridges running along the middle of their upper surfaces and this is typical of the common species A. praetor.

Aleiodes sp. showing ridges on the first two abdominal segments (blue arrows)

I couldn't check this tentative ID myself - at least not without accumulating some articles I don't have ready access to and/or visiting a museum collection (even online there is very little in the way of images, keys and so on). So, I passed this onto some braconid specialists who have confirmed it isn't A. praetor (not orange enough, though there are more technical ID features required too!) and I hope I'll get a definite species ID soon. Until then, I await whatever else appears in the hatchery...

Ventral view of Aleiodes showing orange legs with some black areas, and orange mouthparts.

References

Broad, G. R., Shaw, M.R. & Godfray, H.C.J. (2012). Checklist of British and Irish Braconidae (Hymenoptera) [30th April 2012 version]. Free download here.
Huddleston, T. & Gauld, I. (1988). Parasitic wasps (Ichneumonoidea) in British light-traps. The Entomologist 107(2): 134-154.
Shaw, M.R. & Huddleston, T. (1991). Classification and Biology of braconid wasps (Hymenoptera: Braconidae). RES Handbooks for the Identification of British Insects 7(11): 1-126. Free download here.

A tiny clue that looks like poo

Sometimes a seemingly innocuous observation can lead onto an interesting ecological story... A couple of days ago while collecting bramble and raspberry leaves for my stick-insects, I noticed a small black-and-white cocoon attached to the underside of one of the leaves.

Black-and-white cocoon, 6mm long

Although the occupant has clearly emerged as an adult, I wondered if the distinctive black-and-white cocoon might be identifiable, at least to family level or similar. A quick web search made it clear that this was the pupal cocoon of an ichneumon and it didn't take long to find out that the pattern (which maybe camouflage it as bird-dropping or piece of mould?) is characteristic of the genus Hyposoter (subfamily Camploplaginae).

At least 15 species of this genus can be found in the UK and they parasitise the caterpillars of various butterflies and moths such as the Lymantriidae (tussock-moths), Pieridae (butterflies - whites and yellows) and Lycaenidae (butterflies - coppers, hairstreaks and blues). They do so by the female wasp laying an egg in the host caterpillar, piercing it with her ovipositor. Once hatched, the wasp larva develops inside its host which shrinks, becoming a hard,  brittle shell - effectively mummified. When ready to pupate, the wasp larva spins a cocoon inside the larval skin (or in some cases the host skin splits and the wasp pupates outside) and this creates the black-and-white patchwork pattern - it takes about a month from the egg being laid to a new adult emerging.

I don't know which Hyposoter this is and I doubt that it's possible to tell from just a cocoon. However, one of the British species (H. ebeninus) has been filmed going through its life cycle, and this is certainly a candidate for the species here as the adults match ichneumons I have seen but not identified (though that isn't a reliable indiactor - they are a diverse and tricky group to ID), and parasitises the cabbage white butterfly (Pieris brassicae) which is common here. Again, this is not enough for an identification, but it is something I can look out for next season. In any case, I hope that's an interesting little ecological tale from a passing observation.

Close-up of the Hyposoter cocoon showing silk threads attached to the host's mummified skin.

Multiple cocoon of many mysteries

I'm not often stuck for an identification, at least not for long but while dismantling an old fence panel a few days ago, I did find some things I really couldn't identify, at least maybe not...

Cocoons found attached to an old fence panel

The left-hand one is in some ways the easiest - it's probably a moth, maybe the knot grass (Acronicta rumicis) which I have seen in our garden and which makes long grass-covered cocoons (this one is around 55-60mm long including the grass) - hopefully I'll find out for sure when it emerges as it's now in one of my hatcheries.

The other one is less straightforward. As there's a cigar-shaped cocoon inside it, it is more of a nest than a cocoon as such, and appears to have two concentric 'walls', the inner one thicker and covered in tiny wood fragments.

The 'inner' nest around 18mm long, the cocoon inside is around 8mm long.

The cocoon within the inner nest - whatever was inside has clearly emerged, leaving an open end with a small 'lid'

Next to the cocoon, there's clearly a small black shape, plus in the very top photo, there's material between the two nest walls.

The small black shape turns out to be a dead and shrivelled caterpillar - whatever it was, it bore long hairs/bristles which can still be seen. Length approx. 6mm

From this angle, the true legs can be seen towards the head end (left) curled under the thorax, while the larger, stubby prolegs are more clearly visible in the middle/rear

The relatively simple lens/eye arrangment of the caterpillar

I can't tell what this caterpillar is as it is dry and shrivelled, but the form of the inner nest suggests a puss moth (Cerura vinula) or other member of the family Notodontidae. Mature puss moth larvae are large and spectacular, but the first instar is small and black. However, it doesn't have long bristles, so can't be this species, though other members of the family may be plausible candidates. A different question does arise though - cocoons give rise to adults, not larvae, so what is it doing here? If there were wasp eggs, then one plausible explanation would be that it was brought in immobilised by a solitary wasp as a food source for its own young. However, this is a nest with a cocoon in it, not eggs. Also, there is no evidence of a wasp in the cocoon, but there is the material between the inner and outer nest walls. I am unaware of any wasps where a host caterpillar is entombed by a pupating larva to await its adult emergence, but they are a diverse group  often with complex (and often poorly understood) life-cycles, so I imagine it is possible. Alternatively, the caterpillar was simply caught inside a nest construction and starved.

Spider exuviae (moulted skins) within the outer nest

As seen in the photo above, the material consists mainly of moulted spider skins (exuviae) of differing sizes, sugessting an individual spider grew and moulted several times using the thin outer nest (the red structure top-left is a set of mouthparts, almost as large as the whole skin bottom-right). It seems plausible that the hiding place was a good one and a spider simply used it, building its nest around the tougher one already there. Looking even closer there is more to see.

The thin outer wall and the thck inner wall with wood shavings. Just below where they meet, a small white structure is visible in partial shadow.

Hidden behind the larger structures, what appears to be another, much smaller cocoon. This is now also in a hatchery awaiting whatever emerges.

This looks like an opportunistic cocoon-builder that has just used a handy crevice, but it may be related to the larger nests. I don't know which species are involved, but I hope that the two remaining cocoons remain viable and I'll see which species emerge. You never know, it might shed some light on the mystery nest/larva - and if it does, I will, as ever, post it here.

The widow and the vapourer

While collecting brambles to feed my ever-hungry stick-insects, I noticed a batch of insect eggs on top of a silk mat and tunnel which had knitted two of the leaves together. Of course I had to have a closer look and the eggs were of the vapourer moth Orgyia antiqua, while the tunnel contained a spider which I think is probably one of the Steatoda 'false widows' which are mostly harmless but recently seen in many a tabloid frenzy about deadly spiders - I could probably ID it to species but not without pulling it out of its retreat and I'd rather leave it be as I suspect it found the ready-made moth cocoon to be a handy basis for a web (or maybe it happened the other way around). However the moth eggs do lead onto some interesting biology/ecology.

Vapourer eggs on the female moth's cocoon, under which a spider web/tunnel has been created

Entrance to the spider's retreat - I wonder if the black hairs round the entrance are from a vapourer caterpillar or something else. The flask-shaped moth eggs are clearly visible, including the dark dimple and band at the top.

The spider, probably Steatoda sp. is just visible within

Female vapourers are wingless and do not disperse as adults. Instead when they emerge from their pupal cocoon, they emit pheromones to attract the winged males (they are highly active flying zig-zag routes during the day, and sometimes at night, to find females) and once mated lay their eggs on their old cocoon. The larvae, which feed on various trees and shrubs, are highly distinctive with tufts of yellowish hairs on their dorsal surface and longer, narrower tufts at both ends. The adults are less spectacular and images of them can be seen on the excellent UKMoths site here.

Vapourer moth larva

Vapourer moth larva

Vapourer moth larva